Laudator Temporis Acti

W.H. Auden, Bucolics, 2. Woods, lines 33-36:

And where should an austere philologist
Relax but in the very world of shade
From which the matter of his field was made.

What is the matter of the philologist's field? Words, especially the words found in old books. Perhaps beech trees provide the shade — a philologist would know that there is an etymological connection between books and beeches. See Donald Culross Peattie, A Natural History of North American Trees (Houghton Mifflin Company, 2007), p. 162:

And on the beech was written, probably, the first page of European literature. For, it is said the earliest Sanskrit characters were carved on strips of beech bark; the custom of inscribing the temptingly smooth boles of Beeches came to Europe with the Indo-European people who entered the continent from Asia. Indeed, our word "book" comes from the Anglo-Saxon boc, meaning a letter or character, which in turn derives from the Anglo-Saxon beece, for Beech.

Or is Auden possibily alluding to the Latin adjectives umbraticus and umbratilis? Lewis and Short define umbraticus as "of or belonging to the shade, i.e. to retirement, seclusion, or leisure," and umbratiilis as "remaining in the shade, in retirement, or at home; private, retired, contemplative." The pursuit of philology requires retirement, seclusion, and leisure.

Auden's poem ends with these lines (49-54):

A small grove massacred to the last ash,
An oak with heart-rot, give away the show;
This great society is going smash;
They cannot fool us with how fast they go,
How much they cost each other and the gods!
A culture is no better than its woods.